Food for Thought
Key message: Food is the fuel of the human body,
it keeps us alive and gives us energy.
SESE Curriculu
m Link:
Conte
nt Strand – Livin
g Things
Strand Unit – Hum
an Life
sKILL DEVELOPME
NT:
Experimenting,
observing,
recording, sortin
g and analysing.
Integration Op
portunities:
S
PHE: Myself – Ta
king care of my
body
SESE: History –
Life, society, wor
k and
culture in the pa
st: the Potato Fa
mine
in Ireland
Food for Thought
Key Message: Food is the fuel of the human body, it keeps us alive
and gives us energy.
Before you start
Today we are going to look at food as a fuel for the human body and how it
provides us with energy.
((What do you need to put in a car to make it go?
((What does the petrol give to the car? Energy
((What makes a bicycle go? Energy from cyclist
((Where does the cyclist get energy from? Food
((Where do you get your energy from? Food
((Where does food come from? Plants or animals
((Where did they get their energy from originally? The sun
((How do you usually feel before and after a meal?
((What do sports people eat before an event to have a good store
of energy? Lots of carbohydrates e.g. pasta
((How can we find out which foods give us the most energy?
((Why is it very important for some people to know what foods
contain? Diabetics, coeliacs, allergies
The human body is like a big machine that is always working. Even when
you are asleep you are breathing and your heart is beating. Food is the fuel
which keeps all these things going. We also use large quantities of energy
from food to keep warm. If you eat more food than your body needs then you
store it as fat.
Background
Yeast is a microbe (a tiny living organism which is invisible to the naked
eye, but visible under a microscope) that needs food and heat to live, like all
living things. The yeast feeds on the chemical energy stored in the sugar and
produces the gas carbon dioxide which inflates the balloon.
Foods can be divided into three basic groups: fats, carbohydrates and
protein. Foods rich in carbohydrates are our main source of energy. Sugar
and starch are carbohydrates. Starch is found in plants and also in other
things, e.g. some paper. Pasta, cereals and bread also contain starch.
Food for Thought
How can we see the energy of yeast?
You will need
Dried yeast
Glass bottle
Sugar
Balloon
Jug
Bowl
Steps
1. D
iscuss the function of yeast in bread-making; it does nothing when it
is dry and cold, but when it is warm and wet it feeds off the sugar and
produces the gas carbon dioxide. You can see these bubbles as little
holes in bread.
2. Mix 2 teaspoons of yeast with 2 tablespoons of warm water in the jug.
3. Stir in a teaspoon of sugar.
4. Pour this yeast mixture into a glass bottle and stretch the balloon over
the neck of the bottle.
5. Stand the bottle in a bowl of warm water.
6. Watch what happens the balloon. It inflates! What does this tell us about
yeast? And about bread?
How can we identify starch in food?
You will need
Tincture of iodine (available from chemists) - for teachers’ use only
Small dropper bottles (available from chemists)
Various samples of food, e.g. bread, sugar, pasta, rice, apple, potato,
piece of cheese, orange
Steps
1. P
repare the iodine solution for use by the children. Dilute the tincture
of iodine with water in the ratio of approximately 10:1 water:iodine. If
possible provide one dropper bottle per four children. NOTE: Children
should not be given undiluted iodine
2. S
cientists know that iodine turns dark blue when it meets
starch. Starch contains a good deal of energy and we are
going to test to see which foods contain starch.
3. A
dd a few drops of the iodine solution to each of the food
items and observe the change of colour (if any). Record the
results using the recording sheet.
Food for Thought
Did you know?
The average person walks the equivalent of twice around the
world in a lifetime – quite a lot of food is needed to provide that
amount of energy!
Humans and animals eat other
things (plants or animals) for food,
but plants make their own food.
Sugar cane is grown in
Brazil to make fuel.
During the Potato Famine
in Ireland in the 1840s many
people lost their main source of
energy (the potato) and died as
a result.
Some nutritionists say that junk food affects mental health
and behaviour and that food affects the structure and function
of the brain, i.e. “We are what we eat”.
The Blue Whale needs a million-anda-half calorie diet a day! Humans
need about 2,000 – depending on
their age, lifestyle, etc.
Flies taste their food with
their feet! That is why they
walk all over food before
you eat it. Should you keep
food covered from flies?
Food for Thought
Safety
Care with iodine – close adult supervision; do not get into mouth;
keep away from clothes, iodine stains.
Store the tincture of iodine away from the classroom. Wash hands
after activity.
Discussion
((How can we see the energy of yeast for ourselves? What questions
would we like answered by the experiment? What did
you think would happen? What did happen?
((Which items caused the iodine to change colour? Are these
items similar in any way? What have we learned about these
items of food?
((The children could design a healthy balanced snack. Design and
make a nutritious sandwich for lunch.
((Look at different food packages e.g. cereals, pasta and compare
the amounts of energy in them (could be suitable for a group or
individual project).
((What unit is the energy measured in? kilocalories or kilojoules
((The unit ‘calorie’ has been largely replaced by the ‘joule’ in many
areas of science but ‘calorie’ is still often used in relation to food.
1 calorie and 1 joule are so small that energy in food is usually
measured in kilocalories.
Food for Thought
Recording sheet – photocopy and use
Food:
Bread
Sugar
Pasta
Rice
Apple
Potato
Cheese
Orange
Did the colour of the
iodine change?
Does it contain
starch? Yes or no?